Dopaminergic correlates of motivated behavior: importance of drive

Abstract

In vivo brain microdialysis was used to monitor changes in dopamine (DA) release in the nucleus accumbens (NAc) during anticipatory and consummatory components of feeding behavior. During 10 daily training sessions, rats were first confined to one compartment of a testing chamber for 10 minutes. During this period (anticipatory phase) they were prevented from gaining access to a highly palatable liquid meal by a wire mesh screen. The screen was then removed and the animals were permitted to consume the meal for 20 min (consummatory phase). On removal of the screen, the latency to begin drinking decreased and the amount consumed increased as a function of days of training, both measures reaching asymptotic levels by day 7. Trained animals were implanted with dialysis probes in the NAc on day 10, and on day 12 DA release was monitored during the feeding session. Compared to controls, trained animals failed to show significantly greater increases in accumbal DA release during the anticipatory phase, all groups showing small (approximately 10%) increases on being placed in the test chamber. In contrast, compared to controls, DA release increased significantly in the NAc during consumption of the palatable meal. The magnitude of this increase was significantly enhanced (30% vs 71% peak increase) in animals that were 20 hr food deprived at the time of testing. The latter animals also showed a statistically significant increase (24%) in DA release during the anticipatory phase. A subsequent experiment in which consumption of the palatable liquid was limited to 5 ml in deprived and nondeprived animals indicated that only part of the deprivation-induced potentiation of accumbal DA release could be attributed to the larger volume consumed by the deprived animals. That is, the same volume and rate of consumption of a small amount of the liquid diet produced a significantly greater increase in accumbal DA release in deprived than in nondeprived animals (42% vs 23% peak increase). Feeding-induced increases in accumbal DA release were not due to postingestional factors as direct injections of the liquid diet into the stomach by gavage failed to produce this effect. The results of these experiments indicate (1) that consummatory rather than anticipatory aspects of feeding are robustly associated with increases in DA release in the NAc, and (2) that motivational state can influence the magnitude of the neurochemical events that are associated with goal- directed behaviors.

Escalation in high fat intake in a binge eating model differentially engages dopamine neurons of the ventral tegmental area and requires ghrelin signaling

“…Current results suggest that consummatory rather than anticipatory aspects of feeding are associated with the activation of the mesolimbic pathway. This possibility agrees with previous microdialysis studies showing that Acb dopamine release mainly occurs during the consummatory phase of feeding and not during the anticipatory phase (Sahr et al, 2008;Wilson et al, 1995). Notably, an activation of the MAcbSh neurons was detected in anticipation to the fourth HFD consumption event, similarly as found for the IF dopamine neurons.…”

Effects of Short-Term Abstinence from Escalating Doses of D-Amphetamine on Drug and Sucrose-Evoked Dopamine Efflux in the Rat Nucleus Accumbens

“…In control tests conducted before treatment with either saline or an ED schedule of D-amph, the maximal increase in DA efflux occurred during the first 5 min of the preparatory phase preceding sucrose drinking (preamph group + 45%, presaline group + 49%). A similar pattern of DA efflux also was observed previously only in the first 5 min of the preparatory phase of feeding behavior (Wilson et al, 1995). Together, these findings are consistent with the hypothesis that preparatory aspects of feeding behaviors are preferentially associated with changes in DA metabolism and/or release in the NAc (Blackburn et al, 1989).…”

“…This mesocorticolimbic dopamine (DA) pathway plays a critical role in many aspects of reward, including motivational states triggered by natural incentive stimuli (eg, food, sex, and social interaction) or pharmacological stimuli that can maintain drug self-administration (Everitt et al, 1999;Koob et al, 1998;Wise, 1998). In vivo microdialysis studies in rats report increased DA efflux in the NAc during preparatory and consummatory phases of feeding and sexual behaviors (Phillips et al, 1993;Wilson et al, 1995;Fiorino et al, 1997;Ahn and Phillips, 1999). Furthermore, virtually all drugs of abuse increase DA transmission in the NAc, which partly mediates their rewarding effects (Koob et al, 1998;Wise, 1998).…”

AMPA/kainate, NMDA, and dopamine D1 receptor function in the nucleus accumbens core: A context-limited role in the encoding and consolidation of instrumental memory

“…However, AP-5-treated rats, unlike LY293558-and SCH23390-treated rats, showed no evidence of any additional arousal induced by noncontingent sugar delivery. Indeed, the same low levels of nose-poking were maintained from sessions 2 to 3, which may reflect an inability to act on the arousing effects of elevated levels of dopamine following food delivery (Hernandez and Hoebel 1988;Schultz et al 1993Schultz et al , 1997Wilson et al 1995;Bassareo and Di Chiara 1999). In fact, AP-5 noticeably increased the latency to retrieve rewards (although the sugar was always eaten when found) and lowered the probability of nose-poking after reinforcer delivery, effects not observed after LY293558 or SCH23390 treatment.…”